The aim of this research is to study the effects of nutritional stresses such as EFA deficiency, ingestion of saturated fat diet, diet containing trans fatty acids and diet containing added cholesterol on the growth and lipid metabolism in the developing rat brain. The nutritional stresses are chosen to reflect conditions that are encountered in at least some segments of human populations, although the model is based on the laboratory rat. Competition between excess dietary oleic acid and limiting amounts of linoleic acid first observed by us (G.A.D. & J.F.M. (1961) JAOCS) in adult guinea pigs proved that severe EFA deficiency resulted from such a dietary regime in a very short time. It is proposed to produce EFA deficiency in female rats by this method, prior to mating. Further, the effects of EFA deficiency and other stresses on brain growth and lipid metabolism are to be studied both in the intrauterine and post-natal vulnerable periods. The parameters of this study include determination of brain lipid composition, including fatty acid analysis; uptake and utilization of radioactive precursors such as glucose, acetate, amino acids (such as leucine and isoleucine) and ketone bodies such as B hydroxybutyrate to gain information on lipogenesis. Two other important enzyme reactions, chain elongation and desaturation, that determine fatty acid architecture of brain membranes including myelin will be studied in all animals. It is hoped that the results will help to assemble a composite outline of the effects of nutritional insults on lipid metabolism in the developing brain.